Slashdot Mirror
Sorry, But Lasers Aren't Taking You To Mars Anytime Soon
An anonymous reader writes: It's long been a dream of humanity to travel interplanetary distances at great speeds, or to make it to another star system within a human lifetime. Until recently, technologies to get us there — antimatter propulsion, wormholes or warp drive — have all been composed of physically unrealistic solutions. But recent developments in laser technology make directed energy propulsion a feasible solution. By building a giant laser array in space and developing a new type of solar sail that reflects the laser light with incredible efficiency, a laser sail, this propulsion system is scalable to arbitrarily large powers. There are many technical obstacles to be overcome, and so it's unlikely we'll see the fruit of this anytime in the next few decades (despite the promises of some), but this may well be the technology that takes us to the stars in the coming centuries.
Lasers would get me to Mars faster than I would click on a Forbes link.
Seven puppies were harmed during the making of this post.
Another Ethan Siegel blogspam that will take you to Forbes which HAS BEEN KNOWN TO deliver malware via their adserver. Do not follow the Forbes link!
"Scalable to arbitrarily large powers" = "I haven't thought about this very hard"
Slowing down isn't the problem. Slowing down and staying in one piece is the tricky bit. Just ask the Mars Climate Orbiter team.
"...how would you slow down when you get there? "
Radio ahead to make a deal with the locals to build a similar laser for when you arrive.
XKCD covered this and came to the conclusion that laser propulsion just isn't practical, even by the lofty standards of theoretical intrastellar space travel.
I read the internet for the articles.
Unfortunately you are traveling faster than escape velocity. Therefore you CANNOT "enter orbit". The planet will only deflect your path. The laser idea is just that an idea. Interesting but totally impractical and unworkable. Better to put a liquid salt thorium nuclear reactor and ion drives onboard the space craft. Or use an EM massless drive if it turns out to be real and not an experimental error. The light weight thorium reactor could use both ion drive for long haul low acceleration to conserve reaction mass and for a burst of high acceleration you could use the thermal output of the reactor to heat reaction mass and expel it directly. Interesting idea for a hybrid nuclear rocket system.
Sailing into the wind relies on the keel to resist any sideways motion of the hull so that the only component of force remaining is one which points into the wind. You cannot do that in space. The only way I can think to do anything close to that in space is to use a gravitational field which will be very different to wind-based sailing.
For example no tacking is required: if you want to move closer to the sun use your solar sail to slow your orbital velocity and then just retract the sails and fall. However if you are powered by a laser bank then getting bank to Earth will be a lot trickier since there is no gravitational field to pull you in at inter-planetary distances. You will likely need good timing and rely heavily on complex orbital maneuvers in which case it is hard to see how it is better than a rocket.
If we are talking about sending very small micro satellite or slightly larger sized probes, then who cares about slowing down? You can get good data without slowing down.
I think that disposable probes is where you start. Sending small probes (anywhere) for a few million each to get you to a proof of concept.
Just play with them in Earth orbit to start.
Your link is to a nuclear powered ramjet. Ramjets are air breathing engines and, unless I have been seriously misled, there is a shortage of air between here and Mars. You're probably thinking of nuclear thermal rockets.
I am TheRaven on Soylent News
... Better to put a liquid salt thorium nuclear reactor ... The light weight thorium reactor...
There seems to have developed a nerd cult of the "liquid salt thorium nuclear reactor" which is apparently endowed now with quasi-magical powers, the answer to all possible questions about power sources. The proposed "liquid salt thorium nuclear reactor concept, none of which has every been built, is an idea for large scale fixed power plant designs, and is a very complex system as conceived (involving circulating molten salt fuel, on-line fission product removal systems from the fuel, etc.) that only makes sense - if it is practical at all - as part of a world-wide nuclear power industry. It has absolutely no features of value for a space travel power source.
The notion that such a system could ever be "light weight" is ridiculous - tacking those words on to "thorium reactor" does not make it any sense.
Any real space-flight ready reactor use ceramic highly enriched uranium fuel (negligible hazard until the reactor core turns on for the first time in space), fast neutron operation (moderator is heavy), and as few moving parts as possible. Something more like this.
Starships were meant to fly, Hands up and touch the sky - Nicky Minaj
Seriously? Would you expect me to provide a link if I claimed timecube is bunk?
Actually, yes.
Disclaimer: I'm not the OP or GP or OG or anything like that.
I would expect it because Slashdot is a mixed crowd and some people (GASP!) actually read comments to get a better understanding of what's at hand. You, as a random Slashdotter, have no real standing with me. Not that I dislike you but I don't know you from Adam. You could be making up whatever you talking about or, worse, repeating something from someone else who also is just as clueless but now you've got an idea in your head that you're passing on as facts to others.
Telling someone their wrong in what could be a forward thinking forum would also carry the obligation of explaining why they would be wrong. Any jerk can make flippant remarks and be smug about it but it takes real knowledge to put something out there that will point the way to a better understanding for all involved.
I don't know why people around here think it's such a burden to discuss ideas with one another but is somehow acceptable to bad mouth others on matters that have very defined truths about them.